Queensland parks don't really have seasons is the issue though, it's pretty much just from holiday period to holiday period. The peak seasons are probably the september school holidays and the end of year holidays after christmas. That 3 week period into the new year is probably non negotiable, so december is the deadline.
Trouble is, you can't just make up a schedule with any times you want. With the new government controls in place, you cant exceed the time frame between maintenance intervals. So, say you closed superman for annual maintenance in march 2020, come march 2021, the ride has to close again for yearly maintenance based on the interval. If you want to change the schedule you have two options, close the ride earlier, changing it's yearly rotation, or let the ride sit closed until your maintenance is completed later than the previous year. It has a knock on effect to other rides you might not want closed either.
When you throw in deliveries for major changes, covid and problems with traveling around the world, unexpected ride breakages/failures, and anything else that seeks to completely mess up your planning, there probably isn't much scope for making major changes to your schedule without something being sacrificed. Given the choice of keeping wild west falls closed through later months due to extended works being done, or potentially having to close another major attraction for an extended period of time so you can alter the schedule; there's probably less impact keeping the ride closed and just sucking up the guest complaints about it being shut than there is permanently changing the maintenance schedule for maybe 2 or 3 rides just to cover the extended down time.
I 100% agree with what you are saying, but I know there are probably more things going on behind the scenes than we are aware of that results in scheduling like it does too. Even if its simply down to maintenance budgets only allowing a certain number of employees so your hands are kind of tied with what shutdowns you can manage together due to the workload. A superman may work with a doomsday, a wild west falls with a scooby doo, or a green lantern with a batwing, but a superman and a green lantern, or a superman and a wild west falls might be impossible to manage.